mikejuk writes: A proof has been proposed for the Collatz conjecture about hailstone sequences. A hailstone sequence starts from any positive integer n the next number in the sequence is n/2 if n is even and 3n+1 if n is odd. The conjecture is that this simple sequence always ends in one.Simple to state but very difficult to prove and it has taken more than 60 years to get close to a solution. Paul Erdos said "Mathematics is not yet ready for such problems" — so is it now?